The overall goal of our project is to study the effect of dietary components, such as proteins and fats, and calorie restriction on the incidence of murine mammary tumors, the expression of murine mammary tumor virus (MuMTV) genes and/or gene products, the hormonal status and the immune response in certain high mammary cancer strains of mice (C3H, RIII, GR and GRf). As a result of this investigation we hope to understand how the interaction between MuMTV, hormones and the immune response is altered by the diet, and how these dietary-induced changes affect mammary tumorigenesis in a number of genetically defined strains of mice. Our findings may provide invaluable information that may have some relevance in assessing and correlating the quantitative pathological risk of mammary cancer in humans due to dietary habits.